The plasma membrane presents a major challenge in drug discovery, especially for biologics such as peptides, proteins and nucleic acids. One potential strategy to subvert the membrane barrier and deliver the biologics into cells is to attach them to “cell-penetrating peptides (CPPs)”. Despite three decades of investigation, the fundamental basis for CPP activity remains elusive. CPPs that enter cells via endocytosis must exit from endocytic vesicles in order to reach the cytosol. Unfortunately, the endosomal membrane has proven to be a significant barrier towards cytoplasmic delivery by these CPPs; often a negligible fraction of the peptides escapes into the cell interior (El-Sayed, A et al. AAPS J., 2009, 11, 13-22; Varkouhi, A K et al. J. Controlled Release, 2011, 151, 220-228; Appelbaum, J S et al. Chem. Biol., 2012, 19, 819-830). What are thus needed are new cell penetrating peptides and compositions comprising such peptides that can be used to deliver agents to various cell types. The compositions and methods disclosed herein address these and other needs.